Process for the production of calcium carbamate



Patented May 28, 19 35 ,1 t

UNITEDFSTATES; PATENT OFFICE i l Q 12,002,65 ,7

r'noonss FOR THE PRODUCTION OF CALCIUM CARBAMATE Nikodcm Caro,.Berlin-Dahle m, Albert Rudolph Frank, Berlin-Halensee, and Hans Heinrich Franck, Berlin-Charlottenburg,Germany No Drawing; Application August 22, 1931, Serial Nor-558,848. In Germany. February '8, 1929 V I I V 8 Claims. (Cl. 260 -112) This invention relates to a processfor the proprocess of the invention may be carried into duction of calcium carbamate. efiect:

It is known from the work carried out by A solution of ammonium carbamate is pre- Drechsel (Journal iiir praktische Chemie 1877, pared by saturating a small quantity of water at 5 page 188) that from ammonia water, carbon di- 25 C. under pressure with ammonia and carbon 5 oxide, and milk of lime there can be obtained, dioxide, for example in the proportion of 2:1. by maintaining very strict conditions, a solution A concentrated solution of calcium chloride is from which a certain portion of the lime emthen pumped into this ammonium carbamate ployed can be crystallized out as calcium carsolution whilst still maintained in the same vesbamate by pouring in the same volume of absel the ammonium carbamate being present in 10 solute alcohol at 0 C. This process is only a an amount in excess of that required to comlaboratory one and obviously is not suitable for bine with the calcium chloride. Calcium cartechnical use on a large scale. It has further bamate is imm'edately formed at the temperature been proposed to treat metal salts dissolved in indicated. On coolin the Solution t to liquid ammonia with carbon dioxide and in this about of the Calcium e p oy d 15 way to obtain carbamates is precipitated as carbamate. The excess of According to this invention a particularly sim-. ammonia and carbon dioxide present after the pleprocess of producing calcium carbamate has formation of the calcium carbamate serves to been found which consists in reacting aqueous salt out the calcium carbamate produced. The ammoniacal solutions of ammonium carbamate, o er iquor m y b p y in a cycle by 20 the water content. of which is as low as possible again t a n the Iiquor in h p re v el and which can be saturated with ammonia and With ammonia and Ca b n dioxide or by treatcarbon monoxide or with ammonium carbamate in the qu W th s id ammonium carbamate. by cooling and/or applying pressure or addin Calcium hydroxide, in the form of milk of lime olid a m ni carbamate t temperatures beor suspensions of slaked lime, may be converted 25 tween 40 C. and temperatures at hi h min a similar manner to calcium carbamate. In i m carbamate i till tabl 1, b t; this case the conditions are particularly favour- 2() 3 ith calcium compounds h a 31- able as very highly concentrated solutions of calcium oxide or calcium h d id l i h1 cium carbamate are readily obtained. Calcium ride, calcium nitrate and the like, either in solunit ate may also be employed. tion or in suspension, and cooling the resulting The m sa u d aqu us amm nia al solusomtions, if necessary for example to tions is intended to imply solutions of water in whereby calcium carbamate is precipitated. If ammonia- I the calcium compounds are added in solid form, We Claim: 55 temperatures between 20300 are advisable if 1. A process for producing calcium carbamate 35 it is desired to obtain clear solutions. The temwhich t treaffting satumted g g momaca sou ions 0 ammonium car ama e a reaction proceeds according to the equation: wlth 9 compounds. Soluble m hquld phase, in cooling the solutions and removing cal- C8(OH):+2H2NCOONH4=H2NCOO cium carbama te Ca+2NH OH 2. A process for producing calcium carbamate HzNC O O which consists in treating saturated aqueous ammoniacal'solutions of ammonium carbamate at 4.5 On cooling the solution, resulting from the above temperatures between 40 C, and about .20 C d ub e e p to a low temperature, with suspensions of calcium hydroxide, in cooling cium carbama e Sep at s o n a u t the solutions, and in removing calcium carbampending upon the anions employed and the someate. what varied conditions of solubility. The pres- 3. A process for producing calcium carbamate sure can be either released or the system left which consists intreating saturated aqueous am- 50 under pressure. The salt which separates out moniacal solutions of ammonium carbamate at may or may not contain water of crystallization, temperatures between 40 C. and about -20 C. depending on the water concentration of the amwith suspensions of calcium hydroxide, in ,coolmoniacal mother liquor. ing the solutions to about l0 C., and in remov- The following example illustrates how the ing calcium carbamate.

4. A process as specified in claim 1, wherein the mother liquor from the calcium carbamate separation is reintroduced into the cycle, saturated with ammonia and carbon dioxide in the ratio of about 2 l, and then caused to react with a calcium salt, soluble in the liquid phase, said ammonia and carbon dioxide being employed in a quantity in excess of that required to combine with the calcium salt.

5. A process as specified in claiml, wherein the mother liquor from the calcium carbamate separation is reintroduced into the cycle,"satu-. rated with solid ammonium carbamate, and then caused to react with a calcium salt soluble in the liquid phase, said solid ammonium carbamate being employed in a quantity in excess of that required to combine with the calcium salt;

6. In the production of carbamateof calcium the improvement which comprises causing ammonium carbamate to react with a calcium compound in an aqueous ammoniacal solution, and precipitating the carbamate of calcium by cooling the solution to a temperature below about 10 C.

'7. In the production of carbamate of calcium the improvement which comprises carbonating an aqueous ammoniacal' solution of a calcium compound while maintaining a ratio of CO2 to NH: of 0.5, and precipitating the carbamate of calcium by cooling the solution to a temperature below about 10 C.

8.1In the production of carbamate of calcium theimprovement which comprises adding a calcium compound to an aqueous ammoniacal solution of ammonium carbamate, and precipitating the carbamate'of calcium by cooling the solution to a temperature below about 10 C.

,ALBERT RUDOLPH FRANK.

NIKODEM CARO. HANS HEINRICH FRANCK. 

